Large-amplitude ion acoustic waves in a laser-produced plasma

The frequency and wave number of ion acoustic waves (IAWs), with wave numbers corresponding to stimulated Brillouin scattering (SBS), have been measured as a function of the laser intensity, with time-resolved collective Thomson scattering. At high intensities (I>1013 W/cm2), the scattered light contains a novel component with a large frequency shift, in addition to light frequency shifted by the amount anticipated 2k0cs for SBS-driven ion waves. This is the first observation of large IAWs driven by the interaction laser and not necessarily associated with a parametric instability.